Clinical studies in lymphatic filariasis have defined the persistence of microfilaremia in patients are decades without leading to overt clinical pathology, have identified individuals apparently immune to infection, and have detected subclinical renal and lymphatic pathology in 'asymptomatic' microfilaremic patients. In both loiasis and onchocerciasis, studies on expatriate and endemic populations have defined the hyperresponsive clinical features of the expatriates that contrast with those of endemic populations. Increased diagnostic sensitivity and specificity have been achieved by using PCR-based amplification of parasite DNA is skin snips from patients with onchocerciasis and blood specimens from patients with bancroftian filariasis. Therapeutic trials of ivermectin in bancroftian filariasis have indicated its superiority to diethylcarbamazine as a microfilaricide, and further studies are underway to compare its macrofilaricidal and synergistic activities with DEC. Trials of albendazole in loiasis indicate that this drug appears to be an effective macrofilaricidal and synergistic activities with DEC. Trials of albendazole in loiasis indicate that this drug appears to be an effective macrofilaricide that can be given to patients more safely than DEC.